Memory Refresh Address Generator Reducing Redundancy

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Solution Overview

Problem

As memory cell sizes shrink, the number of memory cells with retention times shorter than the refresh period increases, leading to a higher need for redundancy cells, which in turn increases the size and complexity of volatile memory devices.

Innovation Solution

A method is implemented where a refresh address is generated with a refresh period, and instead of refreshing strong cells, weak cells are refreshed multiple times within the refresh period, using address information to determine when to refresh either a weak cell or a strong cell, thereby reducing the number of redundancy cells needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the number of redundancy cells is increased to accommodate more weak memory cells, then the reliability is improved, but the device complexity and size increase

Engineering Contradiction:

Improvememory cell retention reliabilityVSAvoidredundancy cell array complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of refreshing each weak cell individually when its address is selected, the patent inverts the approach by refreshing a strong cell when a weak cell's address is selected during refresh operations. This allows strong cells to compensate for weak cell data loss, reducing the need for redundancy cells while maintaining reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

Strong cells are given multiple functions: they serve as normal storage cells for their own data and simultaneously act as backup cells for weak cells. This multi-functionality reduces the need for dedicated redundancy cells, decreasing device complexity while maintaining reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If refresh operations are performed more frequently on weak cells, then the reliability is improved, but the power consumption and refresh current increase

Engineering Contradiction:

Improveweak cell data retentionVSAvoidrefresh current consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements self-service by having strong cells automatically refresh data that would otherwise be lost from weak cells during refresh operations. This eliminates the need for additional dedicated refresh operations on weak cells, maintaining reliability without increasing power consumption

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS8873324B2Method of refreshing a memory device, refresh address generator and memory device

Publication Date: 2014.10.28 SAMSUNG ELECTRONICS CO LTD

AI summary

A refresh address is generated with a refresh period for refreshing a memory device with refresh leveraging. A respective refresh is performed on a weak cell having a first address when the refresh address is a second address instead of on a first strong cell having the second address. A respective refresh is performed on one of the first strong cell or a second strong cell having a third address when the refresh address is the third address. Address information is stored for only one of the first, second, and third addresses such that memory capacity may be reduced. In alternative aspects, a respective refresh is performed on one of a weak cell, a first strong cell, or a second strong cell depending on a flag when the refresh address is any of at least one predetermined address to result in refresh leveraging.